1. Field of the Invention
This invention relates to the minimization of pollutants in the air, and, more particularly refers to a new and improved method and apparatus for purifying an air or gas flow of combustible vaporous or gaseous impurities or pollutants by means of adsorption filters.
2. Description of the Prior Art
Purifying an air or gas stream containing combustible vaporous or gaseous impurities by means of adsorption filters in which the air or gas stream is purified and which, after a certain loading with combustible impurities is reached, are desorbed by the counterflow method by means of a hot inert gas generated by stoichiometric combustion of hydrocarbons, and the desorbate carried away by the inert gas burned with added air or oxygen, as well as apparatus suited for the implementation of the method, including two combustion chambers, one of which is connected via a shut-off member to the gas discharge line on the pure-air side and the other, via a further shut-off member, to the gas supply line on the raw-air side, wherein the gas supply line as well as the gas discharge line can be shut off, is described in U.S. Pat. Nos. 3,853,985 and 3,930,803.
The purification of an air or gas stream containing combustible vaporous or gaseous impurities by means of adsorption filters in accordance with U.S. Pat. Nos. 3,853,985 and 3,930,803 was found to be practical and the adsorption filters can be desorbed in a simple and economical manner after they have reached a certain loading. Under certain conditions this procedure has certain disadvantages. In this regard it was also found that inertization by the hot inert gas which is generated by combustion of hydrocarbons in an inert gas generator does not take place fast enough if highly volatile, combustible vapors or gases are adsorbed. In the first place, an increased, undesirable carbon burn-off can be the result; in the second place undesired ignition of the desorbate within the adsorption filter can occur. Also, due to large temperature differences, difficulties were had in maintaining tightness on the shut-off members of the gas supply line and the gas discharge line.